Mechanics

CHEVROLET COBALT ENGINE PROBLEM

2006 Chevrolet Cobalt • 70,000 miles

I have a 2.4L Cobalt I am getting a DTC P1174 Fuel trim adaptation inactive bank 1 malfunction. What do I need to look at? What things trip that code? What is that code saying?
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November 18, 2012.



DTC DESCRIPTOR

DTC P1174
Fuel Trim Cylinder Balance

DIAGNOSTIC FAULT INFORMATION

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection

CIRCUIT/SYSTEM DESCRIPTION
The Fuel Trim Cylinder Balance diagnostic detects a rich or a lean cylinder-to-cylinder air/fuel ratio imbalance. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal's frequency and amplitude characteristics by calculating an accumulated voltage over a predetermined sample period. An imbalance is indicated when multiple samples of the accumulated voltage are consistently higher than the desired value.

CONDITIONS FOR RUNNING THE DTC

DTCs P0030, P0053, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0151, P0152, P0153, P0154, P0155, P0220, P0222, P0223, P0201-P0204, P0300, P0301-P0304, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P060D, P060E, P1133, P1516, P1680, P1681, P2101, P2119, P2120, P2122, P2125, P2127, P2128, P2135, P2138, P2176, P2A00, P2A01, P2A03 are not set.
The device control is not active.
The intrusive diagnostics are not active.
The engine overspeed protection is not active.
The traction control is not active.
The fuel control is in air-fuel Closed Loop.
The system voltage is greater than 10 volts, or less than 18 volts.
The engine run time is greater than 50 seconds.
The engine coolant temperature (ECT) is greater than 10°C (50°F).
The engine speed is greater than 1,000 RPM, but less than 4,000 RPM.
The mass air flow is greater than 7 g/s, but less than 400 g/s.
DTC P1174 runs continuously when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
Multiple samples of the pre-catalyst HO2S accumulated voltage are consistently higher than the desired value.

ACTION TAKEN WHEN THE DTC SETS

The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS

The Fuel Trim Cylinder Balance diagnostic is very sensitive to HO2S design. A non-OE sensor or an incorrect part number may set a false DTC.
Monitoring the misfire current counters, or misfire graph, may help to isolate the cylinder that is causing the condition.

CIRCUIT/SYSTEM TESTING

Read and record the Freeze Frame/Failure Records data taking note of the speed and load at which the DTC set.
Diagnose any other DTCs that are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. See: Diagnostic Trouble Code Descriptions
With the engine idling and the transmission in the Park or Neutral position, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor parameter should be between 19-42 kPa.

If the MAP sensor parameter is not between 19-42 kPa, refer to DTC P0106. See: P0106

Inspect the air induction system for modified, damaged, leaking, or restricted components.
Inspect the crankcase ventilation system for improper operation.
Inspect the vacuum hoses for splits, kinks, and improper connections.
Inspect for vacuum leaks at the intake manifold, the throttle body, and the injector O-rings.
Test for a restricted, damaged, leaking, or modified exhaust system from the catalytic converter forward. Refer to Symptoms - Exhaust System. See: Engine, Cooling and Exhaust\Exhaust System\Testing and Inspection\Symptom Related Diagnostic Procedures
Test the fuel injectors for improper operation. Refer to Fuel Injector Diagnosis. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Fuel Injector Diagnosis
Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Alcohol/Contaminants-in-Fuel Diagnosis
Test for excessive fuel in the crankcase due to leaking injectors.
Test the ignition system for improper operation. Refer to Electronic Ignition (EI) System Diagnosis. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Electronic Ignition (EI) System Diagnosis
Test the engine for any mechanical conditions such as sticking valves, lifters, etc, which could alter the flow into the combustion chamber. Refer to Symptoms - Engine. See: Engine, Cooling and Exhaust\Engine\Testing and Inspection\Symptom Related Diagnostic Procedures

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verify the repair under the same speed and load as noted in the Freeze Frame/Failure Records data recorded during testing.

Air Cleaner Assembly Replacement
Air Cleaner Element Replacement
Air Cleaner Outlet Duct Replacement
Fuel Injector Replacement
Fuel System Cleaning
Fuel Tank Draining Procedure
Ignition Coil(s) Replacement
Intake Manifold Replacement
Spark Plug Replacement
Throttle Body Assembly Replacement

this is the flow chart.

Roy

ASEMaster6371
Nov 18, 2012.